1. Field of the Invention
This invention relates to the field of acceleration detection and processing, and more particularly to an improved method and apparatus for the detection of acceleration forces in any spatial direction.
2. Description of the Prior Art
Detecting accelerations is a widely applied field with applications ranging from object motion to seismic acceleration monitoring. Sensors have therefore been in increasingly high demand. Most devices are designed for a specific purpose and have a particular reason for quantifying accelerations. Multi-direction acceleration sensing has heretofore been possible only by using a complex array of sensing devices whose outputs are processed in a similarly complex electronic processor.
Accordingly, by varying requirements, a need exists for a less complex single sensor device capable of detecting and/or discriminating certain individual acceleration levels, and/or discriminating a targeted spectrum of acceleration(s) as may spatially occur. As well, the need exists to manufacture such a device that may be adapted to a vast array of applications while maintaining a high level of reliability and offering longevity of service, ease of producibility, calibratable results, and low cost of production.
With respect to the world phenomenon known as earthquakes, various alarms and sensors have attempted, with some degree of success, to accurately detect seismic earth tremors for the purposes of warning and/or activating safety measures. Most prior art is particularly sensitive to motion accelerations along an individual plane, resulting in a high ratio of applied spatial acceleration(s) to geometrically triggered response, but only in that plane. However, as specific as seismic tremor waves may be, they may take many forms: complete randomized motions; planar motion; motion askew in any or all three dimensions; purely linear, perhaps vertical with respect to the earth's surface; and combinations of these motions. Additionally, accurate discrimination to only detect particular accelerations, such as caused by earthquakes, separate from other accelerations, such as caused by human intervention, wind, and other forms of vibrations, is difficult.
Most prior art includes a mechanical circuit employing a direct normally open contacting method to form a switching means. Upon the occurrence of an acceleration force, should the planar magnitude of the acceleration component be sufficient, the contacts of the switching means close. This method severely limits the activation characteristics of the system. It further yields a large exposure to environmental or electrical degradation of longevity, with reliability suffering as a result, regardless of the means taken to protect against such degradation.
The embodiment described by U.S. Pat. No. 4,764,762 specifically indicates that the spring's "predetermined range of motion" is "similar to a pendulum swing." A pendulum is constructed as a body suspended from a fixed support so that a weight swings freely back and forth under the influence of gravity, i.e. it pivots at the point of suspension. Though this approach is relatively effective to detect motions in a horizontal (x, y) plane, activity along the vertical (z) axis is ignored. Further, no means, other than the specific limit of an associated spring, controls the fixed ratio of acceleration-to-response, thus rendering this device unable to discriminate within a predetermined response envelope of acceleration, frequency, or other physical parameter involved. It is further limited by a high ratio of vectored x, y acceleration, under the influence of randomly directed accelerations, by the switching means being angularly oriented in the x, y plane.
With respect to object vibration detection, or such, apparatuses of the prior art are usually complicated and extremely costly. Though they may be target specific, most are constructed of single planar sensors mounted individually or in a multi-sensor arrangement aligned in the required planes, such that accelerations may be detected or monitored along one or several planes.
An incorporated means of discrimination, variably to a specific target envelope of acceleration(s), has heretofore not been proposed by the prior art in a single device.